The instant invention relates to two groups of filling materials that find application when used in the manufacture of filled electrical and optical waveguide communications cables.
One group of materials contemplated by this invention is a mixture of organic material and inorganic hollow microspheres having a melting or drip point nearly equal to the melting point of petrolatum, i.e. an average value of 57.2.degree. C. The other group of materials of this invention is composed of a mixture of organic materials and inorganic hollow microspheres having drip points ranging from the drip point of petrolatum per se to 75.degree. C. In this group, the organic material is a modified petrolatum, containing dissolved polyethylene or glycerol hydroxy stearate.
Another aspect of this invention relates to cable filling materials which have desirable dielectric constants and are adapted to occupy the interstices between and around insulated electrical conductors, generally twisted in pairs, forming a bundle or core of a cable.
Another important aspect of this invention relates to communications cables filled with materials, in which entry and migration of moisture within the cable is substantially restricted.
Additional aspects of the instant invention relate to cable filling materials which have reduced shrinkage when cooled and lower dielectric constants and densities than those of petrolatum per se.
Still another aspect of this invention relates to filling materials that can be mixed at approximately 240.degree. F. and used to fill interstices within the communications cables at temperatures ranging from 190.degree. C. to 220.degree. F. during their manufacture.